US8304167B2 - Optical information recording medium - Google Patents

Optical information recording medium Download PDF

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US8304167B2
US8304167B2 US12/494,661 US49466109A US8304167B2 US 8304167 B2 US8304167 B2 US 8304167B2 US 49466109 A US49466109 A US 49466109A US 8304167 B2 US8304167 B2 US 8304167B2
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Prior art keywords
recording
optical information
light
recording medium
information recording
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US20100003447A1 (en
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Yusuke Suzuki
Takao Kudo
Kazuya Hayashibe
Hiroshi Uchiyama
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Sony Corp
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Sony Corp
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/0045—Recording
    • G11B7/00455—Recording involving reflectivity, absorption or colour changes
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/0045—Recording
    • G11B7/00452—Recording involving bubble or bump forming
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/244—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B2007/0003—Recording, reproducing or erasing systems characterised by the structure or type of the carrier
    • G11B2007/0009—Recording, reproducing or erasing systems characterised by the structure or type of the carrier for carriers having data stored in three dimensions, e.g. volume storage
    • G11B2007/0013—Recording, reproducing or erasing systems characterised by the structure or type of the carrier for carriers having data stored in three dimensions, e.g. volume storage for carriers having multiple discrete layers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/244—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only
    • G11B7/245—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only containing a polymeric component

Definitions

  • the present invention relates to an optical information recording medium that is preferably used as an optical information recording medium in which, for example, information is recorded using light beams and is reproduced using the light beams.
  • a disc-shaped optical information recording medium has been widely used, and in general, a compact disc (CD), a digital versatile disc (DVD), a Blu-ray disc (registered trademark, hereinafter referred to as “BD”), and the like have been used.
  • CD compact disc
  • DVD digital versatile disc
  • BD Blu-ray disc
  • an optical information recording/reproducing device using the optical information recording medium described above is designed so as to record various types of information, such as various types of contents including music contents and image contents or various types of data for computers, in the optical information recording medium.
  • various types of contents such as various types of contents including music contents and image contents or various types of data for computers.
  • the optical information recording medium is further desired to have a larger recording capacity.
  • an optical information recording medium in which microscopic holograms formed by interfering light beams of two systems are used as recording marks and are overlapped with each other in the thickness direction of the optical information recording medium so as to record information in one recording layer which corresponds to that recorded in a plurality of layers (for example, see Japanese Patent Application Laid-Open No. 2008-71433).
  • the optical information recording medium disclosed in the above document has the shortcoming in that the optical system thereof is complicated since light beams of two systems are inevitably used.
  • another optical information recording medium has also been proposed in which heat generated by radiated light beams of one system is used to form cavities (air bubbles) in the vicinity of a focus of the light beams, and by using these cavities as recording marks, information corresponding to that recorded in a plurality of layers is recorded in one recording layer (for example, see Japanese Patent Application Laid-Open No. 2005-37658).
  • a drive system may not be easily realized in practice.
  • a continuous-oscillation laser since a high transmittance requested for forming a multilayer structure and a high absorption factor requested in the vicinity of the focus conflict with each other, the absorption factor in the vicinity of the focus may not be significantly increased, and hence, in order to form the recording marks, irradiation may be inevitably performed for a long period of time.
  • the present invention has been conceived in consideration of the problems described above, and it is desirable to provide an optical information recording medium capable of improving a recording rate.
  • a recording layer that has properties of increasing a light absorption amount with respect to the wavelength of recording light when heating is performed at a temperature of 100° C. or more and that absorbs the recording light in accordance with its wavelength, the recording light being condensed for information recording, and increases the temperature in the vicinity of a focus so as to form a recording mark.
  • the recording light can be efficiently absorbed, and the temperature in the vicinity of the focus can be rapidly increased, so that the recording mark can be formed within a short period of time.
  • a recording layer that absorbs recording light in accordance with its wavelength, the recording light being condensed for information recording, and increases the temperature in the vicinity of a focus so as to form a recording mark and that includes an acid generator generating an acid and an acid-reactive compound that is modified by an acid and heat to increase a light absorption amount with respect to the recording light.
  • the recording light absorption amount in the vicinity of the focus can be increased in response to the irradiation of the recording light, the recording light is efficiently absorbed, and the temperature in the vicinity of the focus can be rapidly increased, so that the recording mark can be formed within a short period of time.
  • a recording layer includes a cation generating photopolymerization initiator or a Lewis acid compound, each having a vaporizing temperature in the range of 140° C. to 400° C., and an acid-reactive compound to be modified by an acid generated from the cation generating photopolymerization initiator or the Lewis acid compound described above and that when recording light is condensed for information recording, increases the temperature in the vicinity of a focus of the recording light to vaporize the photopolymerization initiator or the Lewis acid compound so as to form a cavity as a recording mark.
  • the optical information recording medium can efficiently absorb the recording light and increase the temperature in the vicinity of the focus, so that the recording mark can be formed within a short period of time.
  • a recording layer that absorbs recording light in accordance with its wavelength, the recording light being condensed for information recording, and increases the temperature in the vicinity of a focus to form a recording mark and that includes an acid generator generating an acid and a compound having a fluorene structure represented by the following general formula (1).
  • the optical information recording medium since the light absorption amount in the vicinity of the focus can be increased in response to the irradiation of the recording light, the recording light can be efficiently absorbed, and the temperature in the vicinity of the focus can be rapidly increased, so that the recording mark can be formed within a short period of time.
  • the recording light can be efficiently absorbed, the temperature in the vicinity of focus can be rapidly increased, and the recording mark can be formed within a short period of time; hence, an optical information recording medium capable of improving a recording rate can be realized.
  • FIGS. 1A to 1C are schematic views each showing the structure of an optical information recording medium
  • FIG. 2 is a schematic view illustrating irradiation of initializing light
  • FIG. 3 is a schematic view showing photopolymerization initiator residues
  • FIGS. 4A to 4C are schematic views each illustrating irradiation of light beams
  • FIG. 5 is a graph showing the change in light absorption amount by heating with wavelength
  • FIG. 6 is a graph used for illustrating measurement (1) of a vaporizing temperature
  • FIG. 7 is a graph used for illustrating measurement (2) of a vaporizing temperature
  • FIG. 8 is a graph used for illustrating measurement (3) of a vaporizing temperature
  • FIG. 9 is a schematic view showing the structure of an optical information recording/reproducing device.
  • FIGS. 10A and 10B are schematic views illustrating recording and reproducing of information, respectively.
  • FIG. 11 is a graph showing the change in light absorption amount with wavelength.
  • an optical information recording medium 100 is formed, as a whole, such that a recording layer 101 is provided between substrates 102 and 103 so as to function as a medium to record information.
  • the shape of the optical information recording medium 100 is not particularly limited, and of course, a rectangular shape as shown in FIG. 1 may be formed, and a disc having a diameter of 120 mm, such as a general optical disc including a BD (Blu-ray Disc, registered trademark) and a DVD (digital versatile disc), may also be formed to have a clamping hole at the center thereof.
  • BD Blu-ray Disc, registered trademark
  • DVD digital versatile disc
  • the substrates 102 and 103 are formed of glass so as to transmit light at a high rate.
  • the substrates 102 and 103 are formed to have a square shape or a rectangular shape in which a length dx in an X direction and a length dy in a Y direction are set to approximately 50 mm, and in which thicknesses t 2 and t 3 are set to approximately 0.05 to 1.2 mm.
  • An antireflection coating (AR) treatment forming, for example, a four-layer inorganic film (Nb 2 O 5 /SiO 2 /Nb 2 O 5 /SiO 2 ) that is non-reflective to light beams having a wavelength of 405 to 406 nm is performed on outside surfaces (which are not in contact with the recording layer 101 ) of the substrates 102 and 103 .
  • the substrates 102 and 103 various optical materials, such as an acrylic resin and a polycarbonate resin, may also be used as well as a glass plate.
  • the thicknesses t 2 and t 3 of the substrates 102 and 103 are not limited to those described above and may also be appropriately selected outside the range of 0.05 to 1.2 mm.
  • the AR treatment may not be performed on the outside surfaces of the substrates 102 and 103 in some cases.
  • uncured optical information recording medium 100 a an uncured optical information recording medium which contains the liquid material M 1 at a position at which the recording layer 101 shown in FIG. 1 is to be provided.
  • the liquid material M 1 which is to be formed into photopolymers, is provided between the transparent substrates 102 and 103 , so that a thin plate is formed as a whole.
  • a photo-polymerizing or a photo-crosslinking resin material (hereinafter referred to as “photo-curing resin”) forming part or most of the liquid material M 1 contains, for example, radical polymerizable monomers and a radical generating photopolymerization initiator; cationic polymerizable monomers and a cation generating photopolymerization initiator; or a mixture of the above two.
  • the liquid material M 1 in the liquid material M 1 , monomers, oligomers, or a mixture thereof (hereinafter, those mentioned above will be referred to as “monomer(s)”) are uniformly dispersed.
  • the monomers located at a position irradiated with light are polymerized (that is, are photopolymerized) to form photopolymers, and as a result, the refractive index and the reflectance of the liquid material M 1 are changed.
  • the monomers common monomers may be used.
  • the radical polymerizable monomers for example, monomers used for radical polymerization reaction, such as acrylic acid, acrylic acid ester, acrylic amide, and derivatives thereof; and styrene, vinyl naphthalene, and derivatives thereof, may be particularly mentioned.
  • a compound having an acrylic group in a urethane structure may also be used.
  • derivatives of the above-mentioned monomers in which a hydrogen atom is replaced with a halogen atom may also be used.
  • radical polymerizable monomers for example, common compounds, such as acryloyl morpholine, phenoxyethyl acrylate, isobornyl acrylate, 2-hydroxypropyl acrylate, 2-ethylhexyl acrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, neopentyl glycol PO modified diacrylate, 1,9-nonandiol diacrylate, hydroxypivalic acid neopentyl glycol diacrylate, acrylic acid ester, fluorene acrylate, urethane acrylate, octylfluorene, and benzyl acrylate, may be used. These compounds mentioned above each may be a mono-functional or a multifunctional compound.
  • any compounds including an epoxy group or a vinyl group may be used, and for example, common compounds, such as epoxy cyclohexyl methyl acrylate, fluorene epoxy, glycidyl acrylate, vinyl ether, and oxetane, may be used.
  • radical polymerizing photopolymerization initiator for example, common compounds, such as 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, and bis(2,4,6-trimethylbenzoyl)-phenyl phosphine oxide, may be used.
  • cation generating photopolymerization initiator for example, common compounds, such as diphenyliodonium hexafluorophosphate, tri-p-tolylsulfonium hexafluorophosphate, cumyltolyliodonium hexafluorophosphate, cumyltolyliodonium tetrakis(pentafluorophenyl)boron, may be used.
  • diphenyliodonium hexafluorophosphate tri-p-tolylsulfonium hexafluorophosphate
  • cumyltolyliodonium hexafluorophosphate cumyltolyliodonium tetrakis(pentafluorophenyl)boron
  • cured shrinkage of the liquid material M 1 can be decreased as compared to that in the case in which radical polymerizable monomers and a radical generating photopolymerization initiator are used.
  • anionic polymerizable monomers and an anion generating photopolymerization initiator may also be used in combination.
  • a compound having a vaporizing temperature in the range of from 140° C. to 400° C. is preferably used.
  • the reason for this is that in the case of using a photopolymerization initiator having a low vaporizing temperature, when photopolymerization initiator residues present in the vicinity of a focus Fb are heated to an approximately vaporizing temperature or more by irradiation of recording light beams L 2 c , the above residues are vaporized, and as a result, a recording mark RM can be formed.
  • the photopolymerization initiator residues are vaporized by heat generated by the irradiation of the recording light beams L 2 c , and a recording time by a photopolymerization initiator having a low vaporizing temperature actually tends to be shorter than that by a photopolymerization initiator having a high vaporizing temperature, it is also believed that as the vaporizing temperature of the photopolymerization initiator is decreased, the recording mark RM can be more easily formed.
  • an electronic device such as an optical information recording/reproducing device 5
  • a photopolymerization initiator having a vaporizing temperature of 140° C. (80° C.+60° C.) or more is preferably used.
  • a photopolymerization initiator having a vaporizing temperature higher than 140° C. by approximately 5° C. that is, 145° C.
  • the vaporizing temperature of a photopolymerization initiator contained in the liquid material M 1 is preferably in the range of 140° C. to 400° C. and more preferably in the range of 145° C. to 300° C.
  • the amount of the photopolymerization initiator is preferably 0.8 to 40.0 parts by weight and more preferably 2.5 to 20.0 parts by weight with respect to 100 parts by weight of monomers.
  • the liquid material M 1 may also contain appropriate amounts of various additives, such as a polymerization inhibitor that prevents reaction from starting caused by unexpected light and a polymerization promoter that promotes polymerization reaction.
  • the liquid material M 1 is initialized in an initializing device 1 shown in FIG. 2 so as to function as the recording layer 101 recording a recording mark.
  • the initializing device 1 is designed so as to emit the initializing light L 1 (such as a DC (direct current) output of 300 mW/cm 2 ) having a wavelength, for example, of 365 nm from the initializing light source 2 to irradiate the uncured and plate-shaped optical information recording medium 100 a placed on a table 3.
  • the wavelength and the optical power of this initializing light L 1 are appropriately optimized in consideration of the type of photopolymerization initiator used for the liquid material M 1 and a thickness t 1 of the recording layer 101 .
  • a light source capable of radiating high power such as a high-pressure mercury lamp, a high-pressure metal-halide lamp, a solid-state laser, a xenon lamp, or a semiconductor laser, may be used.
  • the initializing light source 2 has a drive portion (not shown in the figure), is able to freely move in an X direction (horizontal direction in FIG. 2 ) and a Y direction (direction perpendicular to the plane of FIG. 2 ), and is also able to uniformly irradiate the uncured optical information recording medium 100 a with the initializing light L 1 from an appropriate position, so that the entire uncured optical information recording medium 100 a is uniformly irradiated with the initializing light L 1 .
  • radicals or cations are generated from the photopolymerization initiator contained in the liquid material M 1 to start a photo-polymerizing reaction, a photo-crosslinking reaction, or both reactions of monomers (hereinafter collectively referred to as a “photoreaction”) and also to advance the photo-polymerizing reaction and the photo-crosslinking reaction of monomers in a chain reaction manner.
  • the refractive index of the recording layer 101 obtained by curing is uniform. That is, even when light is radiated on any position of the initialized optical information recording medium 100 , the amount of returned light is constant, and hence information is not recorded in the optical information recording medium 100 at all.
  • a heat-polymerizing resin material to be polymerized by heat or a heat-crosslinking resin material to be cross-linked by heat may also be used.
  • the liquid material M 1 which is a heat-curing resin in a non-cured state for example, monomers and a curing agent or a heat-curing initiator are uniformly dispersed. Since the monomers are polymerized or cross-linked (hereinafter referred to as “heat curing”) at a high temperature or room temperature, the liquid material M 1 is changed into a polymer, and concomitant with this change, the refractive index and the reflectance are also changed.
  • the liquid material M 1 is formed, for example, by adding a predetermined amount of the above photopolymerization initiator to a curing agent and heat-curable monomers forming a polymer.
  • a curing agent and heat-curable monomers forming a polymer for example, materials which are to be cured at room temperature or a relatively low temperature are preferably used so as not to vaporize the photopolymerization initiator.
  • the heat-curing resin may be cured by heating in advance.
  • monomers used for a heat-curing resin common monomers may be used.
  • monomers used as materials for a phenol resin, a melamine resin, a urea resin, a polyurethane resin, an epoxy resin, an unsaturated polyester resin may be used.
  • curing agent used for a heat-curing resin common curing agents may be used.
  • various curing agents such as an amine, a polyamide resin, an imidazole, a polysulfide resin, and an isocyanate, may be used, and may be appropriately selected in accordance with a reaction temperature and properties of monomers.
  • various additives such as a curing promoter promoting a curing reaction, may also be used.
  • thermoplastic resin material may also be used as the recording layer 101 .
  • the liquid material M 1 spread on the substrate 103 is formed, for example, by adding a predetermined amount of the above photopolymerization initiator to a polymer diluted with a predetermined diluting solvent.
  • thermoplastic resin material common resins may be used.
  • various resins such as an olefin resin, a vinyl chloride resin, a polystyrene, an acrylonitrile butadiene styrene copolymer (ABS), a poly(ethylene terephthalate), an acrylic resin, a poly(vinyl alcohol), a vinylidene chloride resin, a polycarbonate resin, a polyamide resin, an acetal resin, and a norbornene resin, may be used.
  • various solvents such as water, an alcohol, a ketone, an aromatic solvent, a halogenated solvent, and a mixture thereof, may be used.
  • various additives such as a plasticizer changing physical properties of a thermoplastic resin, may also be added.
  • the recording layer 101 preferably has a thickness of 0.05 to 1.0 mm.
  • the total thickness of the substrate 102 transmitting light and the recording layer 101 is preferably set to 1.0 mm or less.
  • the reason for this is that in the case in which the thickness is more than 1.0 mm, the astigmatism of the recording light beams L 2 c generated in the optical information recording medium 100 is increased when the surface thereof is inclined.
  • an unconsumed photopolymerization initiator (hereinafter referred to as “photopolymerization initiator residues”) L is dispersed in spaces A formed in a polymer generated by polymerization of monomers.
  • photopolymerization initiator residues it can also be estimated that unreacted monomers that remain after a curing treatment may be dispersed in the recording layer 101 in some cases.
  • a heat-curing resin or a thermoplastic resin is used as a liquid material, since the photopolymerization initiator is not consumed, the photopolymerization initiator residues L are dispersed in the recording layer 101 as in the case described above.
  • a vaporizing material such as a photopolymerization initiator, a solvent, or monomers, that is vaporized when it is boiled or decomposed at a temperature in the range of from 140° C. to 400° C. (in this case, 140° and 400° are included in the above range, and hereinafter, the range is used in the same meaning as described above), is contained in the liquid material M 1 , a vaporizing material having a vaporizing temperature of 140° C. to 400° C. is dispersed in the initialized recording layer 101 .
  • a vaporizing material such as a photopolymerization initiator, a solvent, or monomers
  • recording light beams L 2 c when predetermined recording light beams L 2 (hereinafter referred to as “recording light beams L 2 c ”) are radiated in the recording layer 101 through an object lens OL, the temperature in the vicinity of a focus Fb of the recording light beams L 2 c is locally increased to a high temperature, such as 140° C. or more.
  • the recording light beams L 2 c vaporize the vaporizing material contained in the recording layer 101 in the vicinity of the focus Fb to increase its volume, so that an air bubble is formed at the focus Fb.
  • the photopolymerization initiator residues vaporized at this time pass through the inside of the recording layer 101 or are cooled when the recording light beams L 2 c are not radiated and returns to a small volume liquid.
  • the recording layer 101 only a cavity formed by the air bubble remains in the vicinity of the focus Fb.
  • a resin forming the recording layer 101 generally transmits air at a predetermined rate, the cavity is eventually filled with air.
  • the recording mark RM which is a cavity made of an air bubble, can be formed at the focus Fb as shown in FIG. 4A .
  • n 101 of a photopolymer used for the recording layer 101 is approximately 1.5, and a refractive index n AIR of air is 1.0, when reading light beams L 2 d are radiated to the recording mark RM, due to the difference in refractive index at the interface of the recording mark RM, as shown in FIG. 4B , the recording layer 101 reflects the reading light beams L 2 d and generates returned light beams L 3 having a relatively large light amount.
  • reading light beams L 2 (hereinafter referred to as “reading light beams L 2 d ”) are radiated to a predetermined target position at which the recording mark RM is not recorded, since the vicinity of the target position has the refractive index n 101 , which is the same index as that of the target position, the reading light beams L 2 d are not reflected as shown in FIG. 4C .
  • the reading light beams L 2 d are radiated to a target position of the recording layer 101 , and the light amount of the returned light beams L 3 reflected by the optical information recording medium 100 is detected, so that the presence of the recording mark RM in the recording layer 101 can be detected, and information recorded in the recording layer 101 can be reproduced.
  • the recording layer 101 of the optical information recording medium 100 is designed such that when heating is performed at 100° C. or more for a predetermined time (such as 1 minute or more), the light absorption properties are changed. That is, the recording layer 101 is formed such that the light absorption amount at the wavelength of the recording light beams L 2 c after heating is large as compared to that before heating.
  • the change in light absorption amount before and after heating is preferably 6.0% or more and more preferably 12.0% or more.
  • This heat absorption change amount is proportional to the thickness t 1 of the recording layer 101 .
  • the heat absorption change amount calculated per 0.1 mm thickness of the recording layer 101 is preferably 2.4% or more and more preferably 4.8% or more.
  • the recording layer 101 can increase the amount of heat generation by improving the light absorption amount in the vicinity of the focus Fb, so that the recording mark RM made of an air bubble can be formed within a short period of time by rapidly increasing the temperature in the vicinity of the focus Fb.
  • the recording layer 101 contains a material in which the light absorption amount at the wavelength of the recording light beams L 2 c is changed by heating.
  • an acid generator generating an acid and a compound hereinafter referred to as “acid-reactive compound” which is modified by an acid and heat to have properties of increasing the light absorption amount with respect to the recording light beams L 2 c are preferably used in combination.
  • the liquid material M 1 contains an acid-reactive compound and an acid generator, the acid-reactive compound and the acid generator are dispersed in the recording layer 101 .
  • the vicinity of the focus Fb is heated by heat generated by the recording light beams L 2 c .
  • an acid generated from the acid generator is present at the focus Fb.
  • the recording layer 101 modifies the acid-reactive compound, so that the light absorption amount of the modified acid-reactive compound with respect to the recording light beams L 2 c can be improved.
  • the modified acid-reactive compound effectively absorbs the recording light beams L 2 c and generates heat, the photopolymerization initiator or the monomers dispersed in the recording layer 101 are rapidly vaporized, so that the time forming a cavity as the recording mark RM in the recording layer 101 can be shortened.
  • either a proton acid generating a proton or a Lewis acid receiving an electron may be used.
  • a strong acid compound such as H 2 SO 4 or HCl
  • an acid having a high acid strength such as RB(C 6 F 5 ) 4 , RSbF 6 , RPF 6 , or RBF 4 (R indicates a general formula); or a compound generating an acid having a high acid strength
  • R indicates a general formula
  • a compound generating an acid having a high acid strength may be preferably used.
  • the acid generators mentioned above each may be present in the state in which its acid is separated or is not separated.
  • a Lewis acid compound generating a Lewis acid may also be used.
  • a cation generating photopolymerization initiator generating an acid in response to heat or light having a wavelength of the recording light beams L 2 c is preferably used.
  • the reasons for this are that cations are generated in response to the irradiation of the recording light beams L 2 c , and in addition, when the recording light beams L 2 c are not radiated, the above photopolymerization initiator does not function as an acid and can prevent degradation of the recording layer 101 caused by an acid.
  • this acid generator in particular, a compound which generates an acid having a high acid strength is preferably used.
  • a compound having a higher acid strength is preferably used, and in particular, compounds generating anion species, such as B(C 6 H 5 ) 4 ⁇ and SbF 6 ⁇ , as shown by the following general formulas (2) to (5) are preferably used. Furthermore, in particular, since antimony, which has a high toxicity, is not contained, a compound (for example, represented by the general formula (2)) generating B(C 6 H 5 ) 4 ⁇ is preferably used. Alternatively, a Lewis acid compound represented by the following general formula (3) may also be contained.
  • the recording layer 101 may contain an appropriate amount of an acid generator in accordance with its acid strength.
  • the acid generator is contained preferably in an amount of 0.7 parts by weight or more and more preferably in an amount of 1.0 part by weight or more. The reasons for this are that an acid-reactive compound can be modified within a short period of time, and that the recording time can be shortened.
  • cation polymerizable monomers may be use; however, cation polymerizable monomers may not be used in some cases.
  • a compound to be rapidly modified by an acid generator and heat is preferably used and may also be contained as part or most of monomers to be polymerized by initialization.
  • a polymer formed by polymerization by the initialization and/or remaining monomers which are not polymerized function as the acid-reactive compound.
  • the acid-reactive compound for example, a compound having a fluorene structure represented by the general formula (1) is preferably used.
  • the acid-reactive compound when a compound having an acrylic functional group, such as an EO (ethylene oxide) modified phenylfluorene compound represented by the general formula (6), is used as the acid-reactive compound, this acid-reactive compound may be used as part or all of monomers to be polymerized by a photoreaction.
  • This acid-reactive compound may also have various functional groups, such as an epoxy group and an ester group, as well as an acrylic group.
  • the acid-reactive compound may be used by adding to monomers.
  • the compound when the compound is solid, the compound may also be used in a manner similar to that for a thermoplastic resin.
  • the acid-reactive compound a compound which has a large heat absorption change amount and which also has properties of increasing the light absorption amount as compared to that before irradiation when light having a wavelength of the recording light beams L 2 c is radiated at a predetermined intensity or more.
  • the reasons for this are that the light absorption amount of the whole recording layer 101 can be increased in response to light energy as well as heat energy, and that by this synergistic effect of light and heat, the recording time can be significantly shortened.
  • the recording layer 101 is formed so as to improve the light absorption amount thereof with respect to the recording light beams L 2 c by heating.
  • the recording layer 101 since the light absorption amount in the vicinity of the focus Fb is increased in response to the irradiation of the recording light beams L 2 c , the temperature in the vicinity of the focus Fb is rapidly increased, so that the recording mark RM made of an air bubble can be formed within a short period of time.
  • Samples S1 to S4 were each formed as the optical information recording medium 100 under the following conditions.
  • Comparative Samples R1 to R4 were each also formed as the optical information recording medium 100 .
  • photopolymerization initiators A, B, D, and E Four types of photopolymerization initiators (shown below) used in Example 1 are represented by photopolymerization initiators A, B, D, and E.
  • the acid generator besides the photopolymerization initiators, a Lewis acid compound C was also used.
  • the polymerization initiators and the Lewis acid compound commercially available compounds were used. Since the polymerization initiators and the Lewis acid compound were commercially available compounds, various additives might also be contained in some cases besides the compounds shown below.
  • Photopolymerization initiator A cumyltolyliodonium tetrakis(pentafluorophenyl)borate (General Formula (2))
  • Photopolymerization initiator B tri(p-tolylsulfonium hexafluoroantimonate (General Formula (4))
  • Lewis acid compound C tri(pentafluorophenyl)boron (General Formula (3))
  • Photopolymerization initiator D bis(t-butyl phenyl)iodonium hexafluorophosphate (General Formula (8))
  • Photopolymerization initiator E 2-hydroxy-2-methyl-1-phenyl-propane-1-one (General Formula (9) shown below)
  • the amounts of the monomers and the photopolymerization initiator forming the liquid material M 1 for each of Samples S1 to S4 and Comparative Samples R1 to R4 are shown in the following table.
  • the photopolymerization initiators A, B, and D were each a cation generating polymerization initiator generating an acid and were blended as an acid generator.
  • the Lewis acid compound C was also blended as an acid generator as with the above photopolymerization initiators.
  • the acrylic acid ester is a p-cumylphenol ethylene oxide adduct acrylate (general formula (10)) shown below, and the fluorene difunctional acrylate is a diphenylfluorene EO modified diacrylate (general formula (6)).
  • the liquid material M 1 was spread on the substrate 103 and was then sandwiched between the substrates 102 and 103 , so that the uncured optical information recording medium 100 a was formed.
  • This uncured optical information recording medium 100 a was irradiated with the initializing light L 1 (having a power density of 42 mW/cm 2 at a wavelength of 365 nm) for 60 seconds using a first initializing light source 1 formed of a high-pressure mercury lamp, so that Samples S1 to S4 and Comparative Samples R1 to R4 each used as the optical information recording medium 100 were formed.
  • the thickness t 1 of the recording layer 101 of each of Samples S1 to S4 and Comparative Samples R1 to R4 was 250 ⁇ m.
  • the light absorption amount of the optical information recording medium 100 was measured using a spectral photometer.
  • the optical information recording medium 100 was placed to be inclined by 5° with respect to a light emission direction of a spectral photometer (V560 manufactured by JASCO Corporation) and was then irradiated with measurement light, and the reflectance and the transmittance of the measurement light with respect to this optical information recording medium 100 were measured at each wavelength.
  • V560 manufactured by JASCO Corporation
  • the irradiation amount of the measurement light was assumed to be 100%, and the reflectance and the transmittance of the measurement light with respect to this optical information recording medium 100 were subtracted from 100%, so that the amount of absorption light of the optical information recording medium 100 which was not heated (hereinafter referred to as “light absorption amount before heating”) was obtained.
  • the optical information recording medium 100 was heated.
  • the optical information recording medium 100 was placed on a heating plate at room temperature (in the range of 20° C. to 50° C.) and was then heated to 120° C. at a rate of 10° C./minute.
  • the optical information recording medium 100 was heated while the heating plate was maintained at 120° C. for 2 minutes and was then cooled to room temperature (23° C.).
  • the optical information recording medium 100 thus heated was called a heated optical information recording medium 100 H and was discriminated from the optical information recording medium 100 which was not heated.
  • the light absorption amount of this heated optical information recording medium 100 H was measured in a manner similar to that for the optical information recording medium 100 , so that a light absorption amount after heating was measured.
  • a heat absorption change amount at a wavelength of 405 nm was calculated by subtracting the light absorption amount before heating at a wavelength of 405 nm from the light absorption amount after heating at a wavelength of 405 nm.
  • the heat absorption change amounts of the optical information recording media 100 (of Samples S1 to S4 and Comparative Samples R1 to R4) are shown below.
  • Atmosphere N 2 (in a nitrogen atmosphere)
  • Measurement temperature 40° C. to 600° C.
  • FIG. 6 shows measurement results of the photopolymerization initiator E used for Samples S1 to S4 and Comparative Samples R1 to R4. According to the DTA curve (shown by the solid line) indicating an endothermic and an exothermic reaction, an exothermic reaction started slightly at approximately 90° C. and occurred vigorously at approximately 120° C.
  • the weight was rapidly decreased at approximately 120° C., and most of the photopolymerization initiator E, which was an object of the measurement, was vaporized at approximately 147° C.
  • a temperature of 147° C. at which the weight was most rapidly decreased was regarded as the vaporizing temperature of the photopolymerization initiator E.
  • FIG. 7 shows measurement results of the photopolymerization initiator A used for Samples S1 and S2 and Comparative Sample R1. According to the DTA curve, an endothermic reaction caused by melting or the like started at approximately 130° C., and an exothermic reaction caused by decomposition or the like started at approximately 230° C.
  • the weight was rapidly decreased at approximately 230° C., and most of the photopolymerization initiator A, which was an object of the measurement, was vaporized at approximately 290° C.
  • a temperature of 290° C. at which the weight was most rapidly decreased was regarded as the vaporizing temperature of the photopolymerization initiator A.
  • the vaporizing temperatures of the other photopolymerization initiators B and D, and the Lewis acid compound C were also measured in a manner similar to that described above. For example, as shown in FIG. 8 , when a measurement object had a plurality of vaporizing temperatures, a lowest temperature (289° C. in FIG. 7 ) at which the weight was rapidly decreased was regarded as the vaporizing temperature of the measurement object.
  • the optical information recording/reproducing device 5 is formed such a way that by radiating light to the whole recording layer 101 of the optical information recording medium 100 , information is recorded in and reproduced from a plurality of recording mark layers (hereinafter referred to as “virtual recording mark layers) supposed in the recording layer 101 .
  • a control portion 6 including central processing units (CPUs) is responsible for integral control of the whole device, and various programs, such as a basic program, an information recording program, and an information reproducing program, are read out from read only memories (ROMs) not shown in the figure and are then developed on random access memories (RAMs) not shown in the figure, so that various processes, such as an information recording process and an information reproducing process, are performed.
  • CPUs central processing units
  • the control portion 6 is formed such that by controlling an optical pickup 7 , light is radiated from the optical pickup 7 to the optical information recording medium 100 , and light that returns from the optical information recording medium 100 is received.
  • the optical pickup 7 is formed in such a way that based on the control by the control portion 6 , light beams L 2 having a wavelength, for example, of 405 to 406 nm are emitted from a recording/reproducing light source 10 made of a laser diode at a DC output, and after being converted from divergent light to parallel light by a collimator lens 11 , the light beams L 2 are made incident on a beam splitter 12 .
  • the recording/reproducing light source 10 is designed so as to be able to adjust the light amount of the light beams L 2 in accordance with the control of the control portion 6 .
  • the beam splitter 12 enables some of the light beams L 2 to pass through a reflection/transmission surface 12 S and to enter an object lens 13 .
  • the object lens 13 is formed so as to condense the light beams L 2 at an arbitrary position in the optical information recording medium 100 .
  • the returned light beams L 3 are converted into parallel light beams by the object lens 13 and then enter the beam splitter 12 .
  • the beam splitter 12 enables some of the returned light beams L 3 to enter a condenser lens 14 by reflection at the reflection/transmission surface 12 S.
  • the condenser lens 14 condenses the returned light beams L 3 and then radiates them to a receiving element 15 .
  • the receiving element 15 detects the light amount of the returned light beams L 3 , generates a detection signal in accordance with this detected light amount, and then sends the detection signal to the control portion 6 .
  • the control portion 6 is designed to be able to recognize the detection state of the returned light beams L 3 based on the detection signal.
  • the optical pickup 7 is provided with a drive portion not shown in the figure and is designed to freely move in three axis directions, an X direction, a Y direction, and a Z direction.
  • the control portion 6 can set the focus position of the light beams L 2 to a desired position.
  • the optical information recording/reproducing device 5 is formed so as to condense the light beams L 2 on an arbitrary position in the optical information recording medium 100 and so as to detect the returned light beams L 3 that return from the optical information recording medium 100 .
  • a target position is set at a depth of 25 to 200 ⁇ m from the surface of the recording layer 101 , and the recording light beams L 2 c , that is, laser light having a wavelength of 405 to 406 nm and an optical power of 55 mW, is emitted from the recording/reproducing light source 10 and is condensed by the object lens 13 having a numerical aperture (NA) of 0.3 to irradiate the target position.
  • NA numerical aperture
  • the optical information recording/reproducing device 5 condenses the reading light beams L 2 d emitted from the recording/reading light source 10 (shown in FIG. 9 ) in the recording layer 101 .
  • the optical information recording/reproducing device 5 controls the position of the optical pickup 7 (shown in FIG. 9 ) in the X direction, the Y direction, and the Z direction, so that the reading light beams L 2 d (shown in FIG. 10B ) is focused on the target position in the recording layer 101 .
  • the reading light beams L 2 d having an optical power of 200 ⁇ W or 1.0 mW and the same wavelength as that of the recoding light beams L 2 c are emitted from the recording/reproducing light source 10 and are condensed by the object lens 13 on the target position in the recording layer 101 at which the recording mark RM is formed.
  • the reading light beams L 2 d are reflected by the recording mark RM and are converted into the returned light beams L 3 .
  • the optical information recording/reproducing device 5 detects the returned light beams L 3 by the receiving element 15 made of a charged coupled device (CCD) through the object lens 13 , the beam splitter 12 , and the like.
  • CCD charged coupled device
  • the optical information recording/reproducing device 5 radiated the recording light beams L 2 c having an optical power of 55 mW and a wavelength of 405 nm to the target position of Sample S1 through the object lens 13 having an NA of 0.3.
  • the time radiating the recording light beams L 2 c from the optical information recording/reproducing device 5 was first set to 1 millisecond and was then increased by 1 millisecond.
  • the optical information recording/reproducing device 5 radiated the reading light beams L 2 d having an optical power of 1.0 mW and the same wavelength as that of the recording light beams L 2 c through the object lens 13 .
  • the receiving element 15 could detect the returned light beams L 3 having a sufficient detectable light amount that returned from the location which was irradiated with the recording light beams L 2 c for 9 milliseconds.
  • the light amount in this step was regarded as a reference light amount, and the recording times for Samples S1 to S4 and Comparative Samples R1 to R4 were measured.
  • the recording layer 101 is preferably formed so as to increase the heat absorption change amount to 6.0% or more and further to 12% or more.
  • photopolymerization initiator A was used as an acid generator for both Sample S1 and Comparative Sample R1, 1.0 part by weight of the photopolymerization initiator A was blended with 100 parts by weight of the monomers in Sample S1, and in Comparative Sample R1, 0.6 part by weight of the photopolymerization initiator A was blended with 100 parts by weight of the monomers.
  • Comparative Sample R1 since the recording time showed a high value of 11 milliseconds as compared to that of Sample S1, it was found that the 1.0 part by weight or more of the acid generator was preferably added to 100 parts by weight of the monomers.
  • Samples S11 to S14 were formed as the optical information recording medium 100 .
  • Comparative Samples R11 to R13 were also formed as the optical information recording medium 100 .
  • Example 2 besides the photopolymerization initiators A, D, and E used in Example 1, one type of photopolymerization initiator (shown below) was used and was referred to as a photopolymerization initiator F.
  • Photopolymerization initiator F bis(t-butyl phenyl)iodonium hexafluoroantimonate (General Formula (5))
  • a fluorene difunctional epoxy is a monomer having the fluorene structure shown by the general formula (1) and two functional epoxy groups (EX1020 manufactured by Osaka Gas Chemicals Co., Ltd.).
  • the light absorption amount of the optical information recording medium 100 was measured by a spectral photometer in a manner similar to that in Example 1, and the light absorption amount of the optical information recording medium 100 before the irradiation of the light (hereinafter referred to as “light absorption amount before irradiation) was obtained.
  • the light was radiated to the optical information recording medium 100 .
  • light having a wavelength of 405 nm emitted from a semiconductor laser was shaped by an anamorphic prism, and only part having a high output was extracted by an iris.
  • the light thus extracted converted into parallel light by a collimator lens and was then radiated perpendicularly to the optical information recording medium 100 for 600 seconds.
  • the diameter of the light radiated on the optical information recording medium 100 was 2.3 mm
  • the light intensity of the light thus radiated was 55 mW
  • the irradiation energy thereof was 800 mJ/cm 2 .
  • the optical information recording medium 100 irradiated with the light is called a light-irradiated optical information recording medium 100 B and is discriminated from the optical information recording medium 100 which is not irradiated with the light.
  • the light absorption amount of this light-irradiated optical information recording medium 100 B was measured in a manner similar to that for the optical information recording medium 100 , so that a light absorption amount after irradiation was measured. Subsequently, by subtracting the light absorption amount before irradiation at a wavelength of 405 nm from the light absorption amount after irradiation at a wavelength of 405 nm, the light absorption change amount at a wavelength of 405 nm was obtained.
  • the light absorption change amount of each optical information recording medium 100 (each of Samples S1 and S11 to S14 and Comparative Samples R3 and R11 to R13) at a wavelength of 405 nm is shown in the following table.
  • Example 2 the vaporizing temperatures of the photopolymerization initiators used in Example 2 were measured in a manner similar to that in Example 1. The vaporizing temperatures are shown in the following table.
  • the recording rates of Samples S1 and S11 to S14 and Comparative Samples R3 and R11 to R13 were measured in a manner similar to that in Example 1.
  • the recording rates of Samples S1 and S11 to S14 and Comparative Samples R3 and R11 to R13 are shown in the following table.
  • the recording layer 101 is preferably formed so as to increase the light absorption change amount to 0.4% or more and further to 2.1% or more.
  • photopolymerization initiator A was used as an acid generator for both Sample S1 and Comparative Sample R11, 1.0 part by weight of the photopolymerization initiator A was blended with 100 parts by weight of the monomers in Sample 1, and in Comparative Sample R11, 0.6 parts by weight the photopolymerization initiator A was blended with 100 parts by weight of the monomers.
  • Comparative Sample R11 Since the recording time of Comparative Sample R11 showed a high value of 11 milliseconds as compared to that of Sample S1, it was found that 0.7 parts by weight or more of the acid generator was preferably blended with 100 parts of monomers, and that 1.0 part of weight or more was more preferably blended therewith.
  • the recording time could be significantly shortened to 0.26 milliseconds as compared to that of Samples S1 and S11 to S13 (recording time: 5.0 to 10.0 milliseconds). It is believed that this effect be obtained because of the structure of octylfluorene.
  • the light absorption change amount of Sample S14 was large, such as 7.5%, as compared to 2.1% to 3.8% of the other Samples S1 and S11 to S13, it was found that when the light absorption change amount was large, the recording time could be further shortened.
  • the recording layer 101 could increase the heat absorption change amount and could shorten the recording time.
  • the photopolymerization initiators A, B, and D generating an acid can be made to hardly contribute to a photoreaction at the initialization stage and can be made to function simply as an acid generator.
  • the photopolymerization initiator A generating an acid was not only used as an acid generator but could also be used as a photopolymerization initiator contributing to a photoreaction at the initialization stage.
  • the recording layer 101 of the optical information recording medium 100 absorbs the recording light beams L 2 c in accordance with their wavelengths, the beams L 2 c being condensed for information recording, and increases the temperature in the vicinity of the focus Fb to form the recording mark RM.
  • the recording layer 101 has properties of increasing the light absorption amount (that is, the heat absorption change amount is large) with respect to the wavelength of the recording light beams L 2 c used as recording light by heating at 100° C. or more.
  • the recording layer 101 in response to the increase in temperature in the vicinity of the focus Fb by irradiation of the recording light beams L 2 c , the light absorption amount with respect to the recording light beams L 2 c can be increased, and the temperature in the vicinity of the focus Fb is rapidly increased by effectively absorbing the recording light beams L 2 c , so that the recording mark RM can be formed within a short period of time.
  • the recoding layer 101 can increase the light absorption amount in a moment in response to light having a high intensity, such as the condensed recording light beams L 2 c , the light absorption amount in a region on which the recoding light beams L 2 c are not radiated (that is, a portion at which the recording mark RM is not formed) is still small, and hence the transmittance of the recording layer 101 can still be maintained high. That is, in the recording layer 101 , although the recording mark RM can be rapidly formed by increasing the light absorption amount in the vicinity of the focus Fb of the recording light beams L 2 c , the recording light beams L 2 c can be transmitted at a high transmittance in the region other than the vicinity of the focus Fb.
  • the recording layer 101 increases the light absorption amount per 0.1 mm thickness thereof by 2.4% or more and preferably by 4.8% or more by heating, energy of the recording light beams L 2 c can be effectively converted into heat, so that the recording time forming the recording mark RM can be further shortened.
  • the recording layer 101 contains at least one of the photopolymerization initiators A, B, and E and the Lewis acid compound C, each having a vaporizing temperature in the range of 140° C. to 400° C.
  • the temperature in the vicinity of the focus Fb of the recording light beams L 2 c is increased to vaporize the at least one of the photopolymerization initiators A, B, and E and the Lewis acid compound C, so that an air bubble as the recording mark RM is formed.
  • the recording layer 101 effectively absorbs light energy of the recording light beams L 2 c by the acid-reactive compound modified by an acid to increase the temperature, the at least one of the photopolymerization initiators A, B, and E and the Lewis acid compound C is rapidly vaporized, and the recording mark RM can be rapidly formed.
  • the recording layer 101 is formed to contain an acid-reactive compound and an acid generator, which are materials increasing the light absorption amount with respect to the wavelength of the recording light beams L 2 c by heating at 120° C. or more.
  • the recording layer 101 when information is recorded, the light absorption amount in the vicinity of the focus Fb can be increased due to a synergistic effect between heat energy and an acid caused by the irradiation of the recording light beams L 2 c , and the recording light beams L 2 c can be efficiently absorbed to rapidly increase the temperature in the vicinity of the focus Fb, so that the recording mark RM can be rapidly formed.
  • the recording layer 101 is formed of a cured resin obtained by photopolymerization of the liquid material M 1 in which monomers, such as monomers or oligomers, and the photopolymerization initiator E as a vaporizing material are at least mixed together.
  • the photopolymerization initiator is excessively contained with respect to the monomers, so that the photopolymerization initiator is allowed to remain in the recording layer 101 obtained by the photopolymerization.
  • the photopolymerization initiator that is excessively contained is vaporized as the temperature in the vicinity of the focus Fb is increased, so that the recording mark RM can be formed.
  • the recording layer 101 contains an acid generator that generates an acid and an acid-reactive compound to be modified by an acid and heat to increase the light absorption amount with respect to the recording light beams L 2 c , and when the recording layer 101 absorbs the recording light beams L 2 c in accordance with their wavelengths, the beams L 2 c being condensed for information recording, and increases the temperature in the vicinity of the focus Fb, the acid generator generates an acid.
  • the recording light beams L 2 c are efficiently absorbed by the modified acid-reactive compound having an increased light absorption amount, and the temperature in the vicinity of the focus Fb is rapidly increased, so that the recording mark RM can be formed within a short period of time.
  • the recording layer 101 contains a cation generating photopolymerization initiator or a Lewis acid compound, each having a vaporizing temperature in the range of 140° C. to 400° C., and an acid-reactive compound to be modified in response to the acid generated from the cation generating photopolymerization initiator or the Lewis acid compound.
  • a cation generating photopolymerization initiator or a Lewis acid compound each having a vaporizing temperature in the range of 140° C. to 400° C., and an acid-reactive compound to be modified in response to the acid generated from the cation generating photopolymerization initiator or the Lewis acid compound.
  • the temperature in the vicinity of the focus Fb can be increased by absorbing a larger number of the recoding light beams L 2 c , so that the recording time forming the recording mark RM can be shortened.
  • the recording layer 101 absorbs the recording light beams L 2 c in accordance with their wavelengths, the beams L 2 c being condensed for information recording, and increases the temperature in the vicinity of the focus Fb so as to form the recording mark RM, and in addition, the recording layer 101 contains an acid generator generating an acid and a compound having a fluorene structure represented by the general formula (1).
  • the compound having a fluorene structure represented by the general formula (1) is modified by an acid generated when the recording light beams L 2 c is radiated, and the light absorption amount of the compound thus modified is increased, so that the recording mark RM can be formed within a short period of time.
  • the recording layer 101 of the optical information recording medium 100 has properties of increasing the light absorption amount in response to heating at 120° C. or more.
  • the light absorption amount with respect to the recording light beams L 2 c can be increased in response to the irradiation thereof, the temperature in the vicinity of the focus Fb is rapidly increased, and the recording mark RM can be formed within a short period of time, so that an optical information recording medium that can improve a recording rate can be realized.
  • the present invention is not limited thereto, and a recording mark in which the refractive index in the vicinity of the focus Fb is changed by a chemical reaction in response to the recording light beams L 2 c may also be formed.
  • the detectable returned light beams L 3 can be generated by reflecting the reading light beams L 2 d by the recording mark.
  • the present invention is not limited thereto.
  • the presence of the recording mark RM may be detected by receiving transmitted light beams of the reading light beams L 2 d , followed by detecting increase and decrease in the light amount thereof.
  • the present invention is not limited thereto.
  • constituent materials of the liquid material M 1 for example, heat-curing monomers, a curing agent curing the monomers, a binder polymer or oligomer, an initiator performing a photopolymerization, and whenever necessary, a sensitizing dye may also be added as long as the photopolymerization initiator is contained in the recording layer 101 obtained by curing.
  • binder component to be added whenever necessary for example, compounds that may be used as a plasticizer, such as ethylene glycol, glycerin, derivatives thereof, and polyalcohols; phthalic esters and derivatives thereof; naphthalene dicarboxylic acid esters and derivatives thereof; phosphoric acid esters and derivatives thereof, fatty acid diesters and derivatives thereof, may be mentioned.
  • a plasticizer such as ethylene glycol, glycerin, derivatives thereof, and polyalcohols
  • phthalic esters and derivatives thereof such as ethylene glycol, glycerin, derivatives thereof, and polyalcohols
  • phthalic esters and derivatives thereof such as ethylene glycol, glycerin, derivatives thereof, and polyalcohols
  • phthalic esters and derivatives thereof such as ethylene glycol, glycerin, derivatives thereof, and polyalcohols
  • phthalic esters and derivatives thereof such as ethylene glycol, glycer
  • the present invention is not limited thereto, and a compound having a vaporizing temperature in the range of 140° C. to 400° C. may also be contained in the recording layer 101 as a vaporizing material.
  • the present invention is not limited thereto.
  • the light absorption amount may also be measured.
  • the present invention is not limited thereto, and for example, one of the photopolymerization initiator and the cured resin may absorb the recording light beams L 2 c to generate heat.
  • a compound other than the photopolymerization initiator such as the cured resin contained in the recording layer and/or an additive to be added whenever necessary, may cause a chemical reaction (such as a combination and/or a decomposition reaction caused by heat or light) in response to the recording light beams L 2 c to generate heat so as to increase the temperature in the vicinity of the focus Fb.
  • the present invention is not limited thereto.
  • a vaporizing material that corresponds to photopolymerization initiator residues forming a cavity by vaporization is contained in a recording layer made of a cured heat-curing resin, and in which a chemical reaction occurs in this recording layer by the initializing light L 1 , the effect equivalent to that of the above embodiment can be obtained.
  • the present invention is not limited thereto, and for example, the initializing light L 1 in the form of diffusion light or convergent light may also be radiated on the optical information recording medium 100 .
  • the present invention is not limited thereto.
  • the initializing light L 1 may be designed to have a different wavelength, or the initializing light L 1 , the recording light beams L 2 c , and the reading light beams L 2 d may be designed to have different wavelengths from each other.
  • the initializing light L 1 have a wavelength sensitive to a photoreaction of a photo-curing resin forming the recording layer 101 , that the recording light beams L 2 c have a wavelength which increases the temperature by thermal conduction of a substance or which is likely to be absorbed, and that the reading light beams L 2 d have a wavelength at which the highest resolution can be obtained.
  • the NA or the like of the object lens 13 FIG. 8 ) may be appropriately adjusted, and furthermore, two types of object lenses optimized for the recording light beams L 2 c and the reading light beams L 2 d may be exchangeably used when the information is recorded and is reproduced, respectively.
  • components and the like thereof may be appropriately adjusted so as to obtain the most preferable properties in combination between wavelengths of the initializing light L 1 , the recording light beams L 2 c , and the reading light beams L 2 d.
  • the recording light beams L 2 c and the reading light beams L 2 d are designed to have a wavelength of 405 to 406 nm
  • the wavelengths thereof may be changed as long as a cavity can be appropriately formed as the recording mark RM in the vicinity of the target position in the recording layer 101 .
  • the present invention is not limited thereto, and the light or the light beams described above may be respectively radiated from any of the two substrate sides or from the two substrate sides, for example, in such a way that the initializing light L 1 is radiated from the substrate 103 side.
  • the optical pickup 7 is moved in the X, the Y, and the Z directions to form the recording mark RM in the recording layer 101 at an arbitrary position that is set as a target position
  • the present invention is not limited thereto.
  • the optical information recording medium 100 is formed as an optical information recording medium such as a CD or a DVD
  • the optical information recording medium may be driven by rotation, and at the same time, the optical pickup 7 may be moved in the X and the Y directions so as to perform recording and reproducing of information.
  • tracking control, focus control, and the like may be performed.
  • the present invention is not limited thereto, and the recording layer 101 may be formed to have other arbitrary dimensions or may be formed to have various shapes, such as a square shape, a rectangular shape, or a rectangular parallelepiped having various dimensions.
  • the thickness t 1 in the Z direction is preferably determined in consideration of the transmittance and the like of the recording light beams L 2 c and the reading light beams L 2 d.
  • the shapes of the substrates 102 and 103 are not limited to a square shape or a rectangular shape, and various shapes may be used in conformity with that of the recording layer 101 .
  • the material for the substrates 102 and 103 is not limited to glass, and for example, polycarbonate may also be used. The point is that any material may be used as long as the initializing light L 1 , the recording light beams L 2 c , and the reading light beams L 2 d can be transmitted therethrough at a relatively high transmittance.
  • the substrates 102 and 103 may be removed from the optical information recording medium 100 .
  • the optical information recording medium 100 functioning as an optical information recording medium is formed of the recording layer 101 functioning as a recording layer
  • the present invention is not limited thereto, the optical information recording medium may be formed using at least one of recording layers having various structures.

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